U.S. patent number 5,421,756 [Application Number 07/893,110] was granted by the patent office on 1995-06-06 for exhaust system for the marine propulsion machine.
This patent grant is currently assigned to Yamaha Hatsudoki Kabushiki Kaisha. Invention is credited to Kenichi Hayasaka.
United States Patent |
5,421,756 |
Hayasaka |
June 6, 1995 |
Exhaust system for the marine propulsion machine
Abstract
The present invention provides an exhaust gas discharge system
for a watercraft. The system has a first discharge path, including
a first outlet, primarily for use during high speed vessel
operation and a second discharge path, including a second outlet,
for use during both low and high speed vessel operation. The first
outlet is arranged to constantly remain below a water surface level
of a body of water within which the watercraft is operated, while
the second outlet is arranged to locate above the water level
surface during high speed vessel operation and to locate below the
body of water, at a level higher than the first outlet, during idle
and low speed vessel operation. Additionally, the second discharge
path has an exhaust flow sectional area of a size at least as large
as the exhaust flow sectional area of the first discharge path. The
system is capable of discharging exhaust gases in a smooth,
efficient manner, and is comprised of a relatively simple
structure.
Inventors: |
Hayasaka; Kenichi (Iwata,
JP) |
Assignee: |
Yamaha Hatsudoki Kabushiki
Kaisha (Shizuoka, JP)
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Family
ID: |
15775729 |
Appl.
No.: |
07/893,110 |
Filed: |
June 3, 1992 |
Foreign Application Priority Data
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Jun 7, 1991 [JP] |
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3-163535 |
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Current U.S.
Class: |
440/89R; 440/89G;
416/93A |
Current CPC
Class: |
F01N
13/005 (20130101); F01N 13/004 (20130101); F01N
13/12 (20130101); B63H 20/245 (20130101); F01N
13/1816 (20130101); B63H 20/22 (20130101); F01N
2530/02 (20130101); F01N 2530/22 (20130101); F01N
2590/02 (20130101) |
Current International
Class: |
F01N
7/12 (20060101); F01N 7/00 (20060101); F01N
7/18 (20060101); B63H 021/32 () |
Field of
Search: |
;440/88,89,900,57-63
;416/9R,9A,93R,93A ;137/216 ;55/DIG.30 ;60/310,311 ;204/147 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1-148695 |
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Jun 1989 |
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JP |
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1-204894 |
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Aug 1989 |
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JP |
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Primary Examiner: Oberleitner; Robert J.
Assistant Examiner: Bartz; Clifford F.
Attorney, Agent or Firm: Knobbe, Martens, Olson &
Bear
Claims
It is claimed:
1. An exhaust system for a drive arrangement of a watercraft,
comprising a first passageway for discharging exhaust gases and a
first outlet located at an end of said first passageway, said first
outlet being arranged to constantly remain below a water surface
level of a body of water within which said watercraft is operated;
a second passageway for discharging exhaust gases and a second
outlet positioned towards an end of said second passageway; wherein
said second outlet is arranged to locate at least partially out of
said body of water during certain operational speeds of the
watercraft; said second outlet being provided with a low degree of
restriction to exhaust gas flow therethrough during said
operational speeds, during which said second outlet locates at
least partially out of said body of water; an ample portion of the
total exhaust gas volume being smoothly discharged via said second
outlet during said operational speeds during which said second
outlet locates at least partially out of said body of water;
wherein said second outlet is further arranged to locate below said
water surface level during other operational speeds of said
watercraft; and wherein said second passageway has an exhaust flow
sectional area of a size at least as large as an exhaust flow
sectional area of said first passageway.
2. The exhaust system of claim 1 wherein said second outlet faces
downwardly; and further comprising an air gap positioned between
said second outlet and said water surface level such that any
exhaust gases which are discharged from said second outlet must
flow through said air gap.
3. The exhaust system of claim 1 wherein the exhaust flow sectional
area of said second passageway is greater than the exhaust flow
sectional area of said first passageway.
4. The exhaust system of claim 1 wherein said second outlet is
positioned along a generally horizontal plane which is vertically
above said first outlet.
5. The exhaust system of claim 1 further comprising an outboard
propulsion unit, said propulsion unit including a propeller mounted
thereupon; wherein said first outlet extends longitudinally through
a hub of said propeller.
6. The exhaust system of claim 5 further comprising a tilt/trim
adjustment system connected to said outboard propulsion unit for
moving said outboard unit about a generally horizontal axis; and
wherein said first outlet includes a portion extending through a
flexible bellows, wherein said bellows permits exhaust gases to
pass therethrough while said outboard unit is moved about said
horizontal axis.
7. The exhaust system of claim 6 further comprising an internal
combustion engine having a circulating coolant water system; and
further comprising an exhaust gas/coolant water mixing region
located within said exhaust system at a position upstream of said
first passageway and whereat a portion of coolant which circulates
through said coolant water system is mixed with said exhaust gases
so that mixed coolant water is able to cool said bellows during
engine operation.
8. The exhaust system of claim 5 wherein said propulsion
arrangement is an inboard/outboard type propulsion system which
includes a gimbal housing and said outboard propulsion unit,
wherein said gimbal housing aids in mounting said outboard
propulsion unit; and wherein said second passageway is formed
through a lowermost portion of said gimbal housing.
9. The exhaust system of claim 8 further comprising a baffle plate,
wherein said baffle plate covers said second outlet and extends up
into said second passageway; wherein said baffle plate is operative
to restrict the effective size of said outlet and to redirect the
flow of exhaust gases emanating from said second outlet in order to
break up the size of exhaust gas bubbles emanating from said second
outlet.
10. The exhaust system of claim 9 further comprising an anode
housed within said baffle plate towards one lateral side thereof
and a reference electrode housed within said baffle plate towards
an opposing lateral side thereof; said anode and reference
electrode comprising portions of an electrical anticorrosion
arrangement.
11. The exhaust system of claim 8 wherein said first passageway is
operational to discharge exhaust gases from said exhaust system
primarily during high speed operation of said watercraft.
12. The exhaust system of claim 11 wherein said second passageway
is operational to discharge exhaust gases throughout a range of
operational speeds of said watercraft; said range including idle
operation, low speed operation and high speed operation.
13. An exhaust system for a drive arrangement of a watercraft,
comprising a first passageway for discharging exhaust gases of a
first outlet located at an end of said first passageway, said first
outlet being arranged to constantly remain below a water surface
level of a body of water within which said watercraft is operated;
a second passageway for discharging exhaust gases and a second
outlet positioned towards an end of said second passageway; wherein
said second outlet is arranged to locate at least partially out of
said body of water during certain operational speeds of said
watercraft; said second passageway being operational to discharge
exhaust gases throughout a range of operational speeds of said
watercraft; said range including idle operation, low speed
operation and high speed operation; said second outlet being
provided with a low degree of restriction to exhaust gas flow
therethrough during said operational speeds, during which said
second outlet locates at least partially out of said body of water;
an ample portion of the total exhaust gas volume being smoothly
discharged via said second outlet during said operational speeds
during which said second outlet locates at least partially out of
said body of water; wherein said second outlet is further arranged
to locate below said water surface level during other operational
speeds of said watercraft; and wherein said second passageway is
provided with a main unrestricted portion and a throttle portion,
wherein an exhaust flow sectional area of said throttle portion is
less than an exhaust flow sectional area of said main unrestricted
portion; however, the exhaust flow sectional area of said throttle
portion is at least as great as the exhaust flow sectional area of
said first passageway.
14. The exhaust system of claim 13 further comprising a plurality
of engine exhaust ports and a pair of manifolds, said manifolds
positioned proximate said exhaust ports to collect exhaust gases
emitted from said exhaust ports; and further comprising a pair of
exhaust gas conduits wherein each one of said conduits leads from a
corresponding one of said manifolds to a single joining pipe
whereat said exhaust gas conduits merge; and further comprising an
exhaust system branching pipe, said exhaust system branching pipe
communicating with said single joining pipe and having a branching
section whereat said first passageway begins and whereat said
second passageway begins; wherein said branching pipe has an
upstream inlet region which has a flow sectional area which is from
70% to 100% the size of the combined flow sectional areas of said
exhaust gas conduits.
15. The exhaust system of claim 14 further comprising an exhaust
gas guide wall formed within said single joining pipe, wherein said
guide wall is operative to help smoothly mix and direct said
exhaust gases which pass into said single joining pipe from said
pair of exhaust gas conduits onward through said exhaust
system.
16. The exhaust system of claim 14 wherein the flow sectional area
of said upstream inlet region of said branching pipe is of a size
approximately equal to the total combined flow sectional areas of
said first passageway and said second passageway.
17. The exhaust system of claim 14 further comprising an arched
wall within said branching pipe which arcs downwardly from a
forward region thereof towards a rearward region thereof, said
arched wall operational to smoothly guide said exhaust gases along
said exhaust system.
18. The exhaust system of claim 16 wherein said second passageway
includes a pair of generally vertically extending passages.
19. The exhaust system of claim 16 wherein said throttled portion
of said second passageway is comprised of a baffle plate; wherein
said baffle plate covers said second outlet and extends up into
said second passageway; wherein said baffle plate is operative to
restrict the effective size of said outlet and to redirect the flow
of exhaust gases emanating from said second outlet in order to
break up the size of exhaust gas bubbles emanating from said second
outlet.
20. The exhaust system of claim 19 further comprising an anode
housed within said baffle plate towards one lateral side thereof
and a reference electrode housed within said baffle plate towards
an opposing lateral side thereof; said anode and reference
electrode comprising portions of an electrical anticorrosion
arrangement.
21. An exhaust system for a drive arrangement of a watercraft,
comprising a first passageway for discharging exhaust gases and a
first outlet located at an end of said first passageway, said first
outlet being arranged to constantly remain below a water surface
level of a body of water within which said watercraft is operated;
a second passageway for discharging exhaust gases and a second
outlet positioned towards an end of said second passageway; wherein
said second outlet is arranged to locate at least partially out of
said body of water during high operational speeds of said
watercraft; means providing said second outlet with a degree of
restriction to exhaust gas flow therethrough, which will permit an
ample portion of the high operational speed exhaust gas volume to
discharge via said second outlet; wherein said means includes a
structural arrangement wherein said second passageway has an
exhaust flow sectional area of a size at least as large as an
exhaust flow sectional area of said first passageway; and wherein
said second outlet is further arranged to locate below said water
surface level during other than high operational speeds of said
watercraft.
22. An exhaust system for a drive arrangement of a watercraft,
comprising a first passageway for discharging exhaust gases and a
first outlet located at an end of said first passageway, said first
outlet being arranged to constantly remain below a water surface
level of a body of water within which said watercraft is operated;
a second passageway for discharging exhaust gases and a second
outlet positioned towards an end of said second passageway; wherein
said second outlet is arranged to locate at least partially out of
said body of water during high operational speeds of said
watercraft; wherein said second outlet is further arranged to
locate below said water surface level during other than high
operational speeds of said watercraft; and wherein said second
passageway is configured to permit a sufficient portion of the
total high operational speed exhaust gas volume to discharge
through said second outlet during high operational speeds so that
the balance of said total high operational speed exhaust gas
volume, which is discharged through said first outlet, is less than
the capacity of the first passageway.
23. The exhaust system of claim 22 wherein said second passageway
has an exhaust flow sectional area at least as large as an exhaust
flow sectional area of said first passageway.
24. The exhaust system of claim 23 additionally comprising a
plurality of engine exhaust ports, at least a first and a second
manifold, said manifolds coupled to said ports to collect exhaust
gases emitted through said exhaust ports, and at least a first and
a second exhaust gas conduit, said first conduit coupling said
first manifold to a joining pipe and said second conduit connecting
said second manifold to said joining pipe, said joining pipe having
an exhaust flow sectional area approximately equal to the combined
exhaust flow sectional area of said first and second
passageways.
25. The exhaust system of claim 24, wherein joining pipe has an
exhaust flow sectional area at least as large as 70% of the
combined exhaust flow sectional areas of said first and second
exhaust gas conduits.
Description
BACKGROUND OF THE INVENTION
This invention relates to an exhaust system for use with a
watercraft propulsion arrangement. More particularly, the invention
relates to an exhaust gas discharge system having one discharge
path primarily for use during high speed vessel operation and
another discharge path for use during both low and high speed
vessel operation. The system is capable of discharging exhaust
gases in a smooth manner, and is comprised of a relatively simple
structure.
The treatment of exhaust gases generated during operation of
watercraft propulsion units, and particularly outboard drives, is a
troublesome one. With particular reference to inboard/outboard
propulsion systems, an exhaust gas discharge system is known which
discharges exhaust gases from an engine, disposed within the
watercraft's hull, through an exhaust passage extending through a
gimbal housing. The gimbal housing is secured to a rearward region
of the watercraft's hull, and aids in supporting an outboard unit
of the inboard/outboard propulsion system. For example, as
disclosed in Japanese Unexamined Patent Publications Hei1-148695
and Hei1-204894, it is known to employ an exhaust passage which
extends alongside an engine mounted within the watercraft's hull.
This passage, in turn, leads to, and communicates with, a further
exhaust passage which extends through a gimbal housing. This latter
exhaust passage branches, at a branching section located within the
region of the gimbal housing, into: (1) a pair of auxiliary
passages which extend downwardly and terminate at outlet openings
located along the bottom of the gimbal housing (for low speed/idle
exhaust); and (2) a main exhaust passage which extends through the
outboard portion of the inboard/outboard system and ultimately
leads to an outlet opening formed through a central portion of an
associated propeller boss (for normal/high speed exhaust).
In the systems just described, at the exhaust passage branching
section located within the region of the gimbal housing, it has
been the practice to utilize a construction wherein the combined
sectional flow area of the pair of auxiliary passages is less than
the sectional flow area of the main exhaust passage. In accordance
with such construction, during low speed and idle operation of the
watercraft the engine exhaust gases are discharged into the body of
water within which the watercraft is being operated through the
pair of auxiliary discharge passages. This is due to the fact that
the outlets associated with these passages are positioned closer to
the body of water's surface, during such operational conditions,
than the outlet of the main exhaust gas discharge passage. On the
other hand, when operating at higher speeds, the engine exhaust
gases are discharged into the body of water via the outlet
associated with the main discharge passage. Such discharge may be
facilitated by a lower pressure region, or pocket, relative to the
pressure existent within the exhaust system, which is generated
behind the propeller boss as the propulsion unit moves through the
body of water.
Such prior exhaust gas discharge arrangements which utilize a main
underwater exhaust passage and an auxiliary discharge system
structured to locate within a body of water at a position which is
not as deeply submerged as the main exhaust passage have employed a
construction wherein the total flow sectional area of the auxiliary
discharge system is less than the flow sectional area of the main
exhaust gas discharge passage. Thus, exhaust gases have been
inhibited from passing through the auxiliary system during
normal/high speed engine operation in such arrangements as a result
of such relative flow sectional area dimensions.
Of course, upon utilizing an engine with a greater number of
cylinders in such an inboard/outboard arrangement, the volume of
exhaust gas produced during high speed operation can increase over
that produced by engines having lower numbers of cylinders. With
such an increase in the volume of exhaust gas produced, it becomes
necessary to increase the flow area of the outlet opening of the
main exhaust passage in order that the exhaust gases might be
smoothly discharged. In order to achieve a through the hub exhaust
outlet which possesses a larger flow area, it is necessary to
increase the diameter of the propeller boss. Such an increase,
however, creates certain problems. For example, an increase in the
diameter of the propeller boss will, in turn, create an increase in
the resistance to fluid flow around the propeller boss, and the
lower casing region of the outboard unit, during movement of the
associated watercraft across the body of water. This increase in
resistance to fluid flow will increase the turbulence about the
main exhaust outlet and will, thus, hinder the smooth discharge of
the exhaust gases.
It is, therefore, a principle object of the present invention to
provide an improved exhaust gas discharge system for a marine
propulsion unit.
It is another object of this invention to provide an improved
exhaust gas discharge system for use in a marine inboard/outboard
drive.
It is yet a further object of the present invention to provide an
exhaust system for a marine propulsion arrangement which is
comprised of a relatively simple structure and which is capable of
discharging a relatively high volume of exhaust gases in a smooth
manner.
As set forth above, it is well known to discharge the exhaust gases
from the powering engine through an underwater exhaust gas
discharge (e.g., through the hub of a propeller) so as to utilize
the body of water in which the watercraft is operating as a
silencing medium. Although this is a very acceptable and effective
way for silencing exhaust gases under high speed running
conditions, it does present certain problems in connection with low
speed exhaust gas discharge. Such problems include a high back
pressure within the exhaust system due to the fact that the
underwater discharge is generally relatively deeply submerged
coupled with the relatively low exhaust pressure generated during
such operation. With an outboard motor, it is the common practice
to provide a separate, above the water, exhaust gas discharge which
has its own silencing system for treating the idling exhaust gases.
With inboard/outboard drives, on the other hand, the powering
engine usually has a larger displacement and the treatment of the
exhaust gases during idling presents different problems. As
depicted in the above-discussed exemplary arrangements, it has been
known to employ a further auxiliary exhaust gas discharge which is
also underwater when the boat is traveling at low speeds but is
less deeply submerged than the high speed exhaust gas discharge.
The prior arrangements utilizing such an auxiliary exhaust gas
discharge have been designed so that the auxiliary discharge has a
smaller flow sectional area than the main underwater exhaust gas
discharge, thereby preventing exhaust gases from passing through
the auxiliary system during normal/high speed engine operation.
Although generally these arrangements do provide good silencing,
the low speed/idle exhaust gases tend to emanate in large bubbles
which can cause objectionable noise.
It is, therefore, still a further object of this invention to
provide an improved silencing arrangement for the exhaust gases of
an inboard/outboard drive unit.
SUMMARY OF THE INVENTION
The present invention is adapted to be embodied in an exhaust
system for a drive arrangement of a watercraft. The invention
includes a first passageway for discharging exhaust gases and a
first outlet located at an end of the first passageway. The first
outlet is arranged to constantly remain below a water surface level
of a body of water within which the watercraft is operated. A
second passageway for discharging exhaust gases and a second outlet
are also provided. The second outlet is positioned towards an end
of the second passageway and is arranged to locate at least
partially out of the body of water during certain operational
speeds of the watercraft, thereby providing the second outlet with
a degree of restriction to exhaust gas flow therethrough which will
permit a substantial portion of the total exhaust gas volume to
discharge via the second outlet during such operational speeds. The
second outlet is further arranged to locate below the water surface
level during other operational speeds of the watercraft.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevational view, of a watercraft, shown in part
and with portions broken away and portions shown in phantom,
powered by an inboard/outboard drive constructed in accordance
with, and embodying, the present invention.
FIG. 2 is a plan view from beneath the watercraft of the invention
showing portions of the electrical anticorrosion arrangement and an
auxiliary exhaust gas discharge region.
FIG. 3 is a sectional view taken along the line 3--3 of FIG. 1.
FIG. 4 is a sectional view taken along the line 4--4 of FIG. 3.
FIG. 5 is a sectional view taken along the line 5--5 of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now in detail to the drawings, and initially to FIG. 1, a
watercraft powered by an inboard/outboard drive constructed in
accordance with the present invention is shown in part and is
indicated generally by the reference numeral 12. The watercraft is
comprised of a hull 14 in which an internal combustion, V-type,
multi-cylinder engine 16 is positioned via engine mounting units
17. The engine 16 drives an engine output shaft 18 which leads to
an outboard drive unit indicated generally by the reference numeral
20.
An intermediate unit 21 is located between the engine 16 and the
propulsion unit 20. The intermediate unit 21 is comprised of a
number of components, including a transom plate or gimbal housing
23 that is adapted to be affixed, in a known manner, to a transom
25 of the associated watercraft 12. A gimbal ring 26 is affixed to
the gimbal housing 23 and is supported for steering movement about
a generally vertical steering axis defined by upper and lower pivot
shafts 28 and 29, respectively.
The gimbal ring 26 is provided with a pivotal connection 32, at a
point along the length of the gimbal ring 26, which defines a
generally horizontally extending axis about which the propulsion
unit 20 may be pivoted between a plurality of trim and tilt
adjusted positions. Such tilt and trim movement of the drive 20
relative to the gimbal ring 26 is controlled by means of a
hydraulically operated cylinder assembly 34, with one cylinder
located towards each lateral side of the propulsion unit 20 (See
FIG. 2). The cylinder assembly 34 includes cylinder units 36 and 38
which are connected to a lower portion of the gimbal ring 26 at one
end by means of a pivot shaft 42. A piston rod 44 of each cylinder
has a trunion portion 46 that is connected by means of a pivot pin
48 to a rearwardly located portion of an upper casing 49 of the
housing of the propulsion unit 20. An oil distributor unit 52 is
provided for supplying pressurized fluid from an inboard mounted
reversible electric motor, pump and control circuit to the fluid
chambers within each cylinder (36 and 38) in response to control
signals which indicate the tilt or trim position which is desired.
As a result, movement of the piston rods 44 will effect pivotal
movement of the housing assembly of the propulsion unit 20 about
the connection 32.
With particular reference to FIG. 1, it can be seen that the output
shaft 18 extending from the engine 16 is coupled to an input shaft
54 of a transmission arrangement for the outboard drive unit 20.
The input shaft 54 can selectively drive a driveshaft member 56 by
means of a forward, neutral, reverse transmission arrangement,
indicated generally by the reference numeral 58. The drive imparted
to the driveshaft 56 is transmitted to a propeller shaft 59 by way
of a bevel gear arrangement 62 located in a lower casing portion 64
of the outboard unit 20. A propeller 66, including a cylindrical
boss portion 68 and outwardly extending blades 72, is fixed along
the rearward end of the propeller shaft 59. A rubber damper 67 is
interposed between the propeller shaft 59 and an inner portion of
the propeller 66. The propeller 66 is powered selectively via the
transmission arrangement 58 so as to propel the associated
watercraft 12 across a body of water.
The internal combustion engine 16 is provided with a plurality of
exhaust ports 74, of which one bank is illustrated in FIG. 1.
Specifically, the engine 16 is V-shaped with one bank of four
cylinders (and corresponding exhaust ports 74) located towards each
lateral side thereof; thus, the embodiment depicted in the Figures
has a total of eight cylinders. An exhaust manifold 76 is provided
across each bank of cylinders and acts to collect exhaust gases
emitted from the exhaust ports 74. The engine exhaust gases
produced during operation of the engine 16 (indicated by the white
arrows) flow from each manifold 76 into a respective conduit 78
extending upwardly of, and rearwardly along, the engine 16, and
then into a Y pipe having branched exhaust passages 82 which are
connected to the respective conduit 78 which is located along the
same lateral side of the engine 16 as the respective exhaust ports
74.
As is typical with marine practice, a coolant jacket 79 surrounds a
substantial portion of the length of each exhaust gas conduit 78.
Water coolant, which is circulated through selected portions of the
engine 16 for its cooling during its operation, is introduced into
the jackets 79 at a location proximate the exhaust ports 74, as
indicated by the blackened arrows of FIG. 1. The coolant flows
along the outer perimeter of the conduit 78 until it reaches a
rearward region thereof. At this rearward region the coolant water
is mixed with the exhaust gases at a mixing area 81.
Now, referring additionally to FIGS. 3 and 4, it can be seen that
the exhaust passages 82, which extend rearwardly and downwardly
along each side of the engine 16, merge at their rearwardmost
regions into a common joining pipe 84, which extends from a
location slightly behind the engine 16 towards the rear of the
watercraft 12. A curved protrusion formed midway along the lateral
width of the joining pipe 84, and having an apex which extends
rearwardly therein, comprises a guide wall 86 which acts to direct
the exhaust gases so that they enter the joining pipe 84, and
continue to travel through the exhaust system, in a smooth
manner.
An exhaust pipe 88 is connected to a rearwardmost end of the
joining pipe 84. An O-ring 85 is interposed between the abutting
ends of the two pipes 84 and 88 so that the connection between them
is maintained watertight. The exhaust pipe 88 is formed within a
central region of the gimbal housing 23. It is within this exhaust
pipe 88 that the exhaust system branches, at a branching region 89,
into two portions; namely: (1) a main passageway 92 utilized
primarily during normal and high speed vessel operation; and, (2)
an auxiliary passage arrangement 94. The branching section 89 is
defined by an upstream opening 87 of the pipe 88, whereat the pipe
88 abuts the rearwardmost end of the joining pipe 84; an upstream
inlet 91 which constitutes the beginning of the main exhaust gas
passageway 92, and which is located rearwardly of the upstream
opening 87; two inlet openings (106 and 108) of the auxiliary
passage arrangement 94, wherein one of such openings is located
towards each lateral side of the inlet 91; and a plurality of inner
wall surfaces interconnecting these structures. One such wall
comprises an arched wall 93 which bridges the region between an
upper portion of the opening 87 and a lower portion along the
region of the inlet 91, as best seen in FIGS. 3 and 4.
The main passageway 92 begins along a rearwardmost portion of the
exhaust pipe 88, at the upstream inlet 91, and continues rearwardly
through the gimbal housing 23 into a flexible, tubular, bellows 96.
The bellows 96 is constructed of any suitable rubber material. A
forwardly located, flattened, cylindrical, end portion of the
bellows 96 connects to a rearwardly located end portion of the pipe
88 via an overlapped region between the inner circumference of the
bellows 96 and the outer circumference of the pipe 88, as shown in
the Figures. The other end of the bellows 96 is also provided with
a flattened, cylindrical, end portion. This second end of the
bellows 96 is connected to a further exhaust pipe 98, which
similarly constitutes a portion of the main exhaust passage 92 and
constitutes a part of the propulsion unit 20, and which is situated
longitudinally through the swivel bracket 24. Specifically, the
bellows 96 connects to an end portion of the pipe 98 via an
overlapped region between the inner circumference of the bellows 96
and the outer circumference of the pipe 98. As best seen in FIG. 3,
a pair of hose clamps 102 secures the bellows 96 in place between
the two exhaust pipes 88 and 98. The flexible bellows 96 allows the
propulsion unit to move about its tilt/trim axis, while maintaining
the integrity of the main exhaust passage 92 so that exhaust gases
may continue to smoothly pass therethrough.
As best seen in FIGS. 1 and 3, the main exhaust passage 92
continues rearwardly from the pipe 98 back into the upper region 49
of the outboard unit 20. As shown in FIG. 1, the passage 92 turns
downwardly, at a location rearward of the drive shaft 56, and
continues into the lower region 64 of the outboard unit 20. The
main passage 92 then turns rearwardly and runs along the propeller
shaft 59 and is provided with an exhaust gas outlet 104 which
extends through the boss 68 of the propeller 66, and which
terminates at the rearwardmost portion thereof.
The through the hub exhaust gas discharge opening 104 is extremely
effective in silencing the high speed exhaust gases from the engine
16. However, when operating at lower speeds, or during idle, the
degree of submersion of the underwater high speed discharge 104 is
too great to allow idling gases to readily pass therethrough, and
the back pressure of the idling gases of the engine 16 will be so
high as to impede efficient operation of the propulsion
arrangement. For that reason, there is provided an auxiliary
exhaust gas discharge 94, which is described below.
The auxiliary passage arrangement 94 branches downwardly from the
exhaust pipe 88 at the branching region 89 thereof. Specifically,
as shown in FIG. 3, a pair of openings 106 and 108 are formed, with
one such opening formed to each lateral side of the exhaust pipe
88, through the exhaust pipe's 88 lower wall. These openings 106
and 108 comprise respective upstream inlets for a pair of
corresponding, downwardly extending, auxiliary exhaust pipes 112
and 114 (See FIG. 5). The auxiliary exhaust pipes 112 and 114, in
turn, terminate in a pair of respective auxiliary exhaust gas
outlets 116 and 118 formed through the bottom region of the gimbal
housing 23. It should be noted, as is readily apparent upon viewing
FIG. 1, that the auxiliary exhaust gas outlets 116 and 118 are
located closer to the surface of the body of water within which the
watercraft is operated than the main exhaust gas outlet 104.
According to this overall construction of the exhaust system, the
exhaust gases which have mixed with an amount of coolant water at
the mixing region 81 pass downwardly through each of the exhaust
passages 82 and continue on into the exhaust pipe 88 within the
gimbal housing 23. Dependent upon the current operating conditions,
a portion of the exhaust gas/coolant water mixture may pass through
the main exhaust system 92 and discharge out of the outlet 104, and
a portion of the exhaust gas/coolant water mixture may pass through
the auxiliary exhaust system 94 and discharge out of its outlets.
The coolant water of that portion which passes through, and is
discharged from, the main exhaust gas system 92 will act to cool
the rubber bellows 96 and the rubber damper 67, which components
are located along such system. This cooling effect helps to
preserve the useful life of these components.
The construction just described is intended, in part, to provide
exhaust gas silencing for low speed or idle running. However, the
discharge of the idling gases causes rather large exhaust gas
bubbles to form which are noisy when breaking up. Accordingly, the
present invention provides a baffle plate member, indicated
generally by the reference numeral 122, mounted across the outlet
openings 116 and 118 in order to break up these bubbles and to
provide effective silencing. General details of a known auxiliary
exhaust gas outlet and baffle arrangement are set forth in U.S.
Pat. No. 4,957,461 to Nakayama.
As may best be seen in FIGS. 2 and 5, the baffle 122 is comprised
of a pair of exhaust gas receiving openings 124A and 124B which are
generally. aligned, and register, with the discharge openings 116
and 118. The lower face of the baffle 122 is formed with a
plurality of projecting ribs 126A and 126B that define a number of
pockets which, in effect, provide a labyrinth type device so that
the exhaust gases must flow through a plurality of the pockets
before they can enter into the body of water, via multiple outlets
123A and 123B, in which the watercraft 12 is operating. As a
result, the exhaust gas bubbles will be broken up into very small
sizes and their rupturing will not cause an objectionable sound. In
addition, the use of the baffles formed by the ribs 126A and 126B
provides additional silencing by itself, apart from the breaking up
of potentially large exhaust bubbles, so as to insure against
objectionable noises during idling. The baffle plate 122 is formed
with a plurality of openings that are adapted to pass threaded
fasteners 128 so as to afford a means of attachment to the
underside of the gimbal housing 23.
The baffle plate 122 serves an additional function as an electrode
case for an anti-corrosion electrode arrangement of the present
invention; thus, the term "electrode case" as employed hereinafter
refers to element 122, as does the term "baffle plate" as employed
above.
The electrode case 122 is formed of any suitable resin material,
and includes an insulating material comprising the regions thereof
denoted by the reference numerals 132 and 134 whereat compartments
for housing the electrodes, described below, are located. An anode
136 is positioned to a lateral side of the electrode case 122
proximate the region 132. A reference electrode 138 is positioned
to the other lateral side of the electrode case proximate the
region 134.
The anode 136 is held within a compartment 142 defined, in part, by
the surrounding regions of the electrode case 122. The reference
electrode 138 is similarly held within its own compartment 144.
Each of these compartments 144 and 142 is provided with a set of
openings 146A and 146B which allow water to flow in and out of the
compartments 144 and 142 housing the reference electrode 138 and
the anode 136.
A lead wire 148 communicating with the anode 136 and a lead wire
152 communicating with the reference electrode 138 extend from
their respective electrodes generally horizontally across the
electrode case 122, and subsequently turn upwardly and extend
through the central region of the electrode case 122. A rubber
cover member 154 is embedded within the electrode case 122 directly
beneath the lead wires 148 and 152 along the region at which the
lead wires 148 and 152 begin their vertical ascent. The lead wires
ultimately connect to the current control circuit of a control unit
(not shown) at their ends remote from the ends which connect to the
electrodes 136 and 138. The control unit senses the potential
difference between the reference electrode 138 and the material to
be protected and determines the proper electrical current necessary
to supply to the anode 136 so that corrosion of such protected
material may be prevented. A suitable control unit for effecting
the prevention of corrosion in such a system is disclosed in
copending U.S. patent application Ser. No. 07/833,090 filed on Feb.
10, 1992 by Kuragaki.
The gimbal housing 23 and the gimbal ring 26 are electrically
connected via a conductive wire 158, as shown in FIG. 2. The gimbal
ring 26 and the swivel bracket 24 are electrically connected via a
further conductive wire (not shown). Accordingly, the components of
the intermediate unit 21 and the propulsion unit 20 are in
electrical communication with one another. In this way, both of
these assemblies essentially share a common potential and are
afforded cathodic protection by the arrangement of the
invention.
Advantages provided by the construction of the cathodic protection
arrangement set forth above include the fact that when the
propulsion unit 20 is disposed so that its longitudinal axis is
generally perpendicular to the plane of the transom 25, the
distance from the anode 136 to the propulsion unit 20 is
essentially the same as the distance from the reference electrode
138 to the propulsion unit 20. Therefore, the current necessary to
supply to the anode 136 in order to maintain the desired potential
for the most effective cathodic protection will be readily
determinable. Additionally, the possibility of inadvertently
supplying an excessive amount of current to the anode 136 can be
avoided, since the control circuit assembly will have an accurate
indication of the actual present potential at the material to be
protected. Furthermore, the electrode case 122 is readily removable
via the threaded fasteners 128 for easy access when servicing or
the like is required.
As set forth above, the prior exhaust gas discharge arrangements
which utilize a main underwater exhaust passage and an auxiliary
discharge system structured to locate within a body of water at a
position which is not as deeply submerged as the main exhaust
passage have employed a construction wherein the total flow
sectional area of the auxiliary discharge system is less than the
flow sectional area of the main exhaust gas discharge passage.
Thus, exhaust gases have been inhibited from passing through the
auxiliary system during normal/high speed engine operation in such
arrangements as a result of such relative flow sectional area
dimensions.
With reference once again to the Figures as they relate to the main
and auxiliary exhaust gas discharge systems (92 and 94,
respectively), the present invention provides an arrangement
wherein the combined flow sectional areas of the two passages 112
and 114 of the auxiliary discharge system 94, from inlets 106 and
108 at the branching region 89 to the outlets 116 and 118, is
structured to be approximately equal to, or greater than, the flow
sectional area of the main discharge system 92, from the inlet 91
at the branching region 89 to the main outlet 104.
More specifically, as contemplated by the present invention, where
a1 and a2 denote the flow sectional areas of each of the two
exhaust passages 82 which extend rearwardly and downwardly along
each side of the engine 16, respectively; and where b denotes the
area of the upstream opening 87 of the pipe 88; b is structured to
comprise a quantity approximately equal to, or any quantity down to
about 70% of, the quantity defined by the sum of the areas a1 and
a1. Further, where c1 and c2 denote the flow sectional areas of the
two passages 112 and 114, respectively, of the auxiliary discharge
system 94; and where d denotes the flow sectional area of the main
discharge system 92, from the inlet 91 to the main outlet 104, the
following relationships are observed:
The outlets 123A and 123B of the auxiliary exhaust gas system 94
are arranged so that they are positioned higher than the surface
level of the body of water within which the watercraft 12 is
operated, at least during high speed operation of the vessel. This
water level is indicated by the reference character L1. Thus, under
such operating conditions, the outlets 123A and 123B are located
opposite the water surface level L1, as shown in FIG. 1. The
outlets 123A and 123B of the auxiliary exhaust gas system 94 are
arranged so that they are positioned below the surface level of the
body of water within which the watercraft 12 is operated at low
speed or during idle. This water level is indicated by the
reference character L2. Accordingly, under low speed and idle
operating conditions the outlets 123A and 123B are located beneath
the water surface level L2.
The main exhaust gas discharge outlet 104 of the main discharge
system 92 is arranged so that it always remains beneath the surface
level of the body of water within which the watercraft 12 is
operated under all operating conditions (i.e., from idle to high
speed operation).
Each of the auxiliary outlets 116 and 118 of the passages 112 and
114 are provided with throttle arrangements 162A and 162B. The
total combined flow sectional areas of the throttle arrangements
162A and 162B are arranged to be less than that of the exhaust
passages 112 and 114. These throttle arrangements 162A and 162B are
integrally formed with the electrode case/baffle plate structure
122. Specifically, the throttle arrangements 162A and 162B comprise
a plurality of small passageways, with their boundaries being
defined by the ribs 126A and 126B.
More specifically, as contemplated by the present invention, where
g1 and g2 represent the combined sectional areas of the ribs 126A
and 126B themselves, respectively; and where e1 and e2 comprise the
combined flow sectional areas of the outlets 123A and 123B,
respectively; the following relationships are observed:
(1) c1-g1=e1; and,
(2) c2-g2=e2.
According to the construction set forth above, the relationship
between the flow sectional areas e1 and e2 of the outlets 123A and
123B and the flow sectional areas c1 and c2 of the auxiliary
exhaust system passages 112 and 114 is as follows:
(1) e1<e1; and,
(2) e2<c2.
Additionally, the relationship between the flow sectional areas e1
and e2 of the outlets 123A and 123B and the flow sectional area d
of the main exhaust system 92, from the branching area 89 to the
main exhaust outlet 104, is set as follows: (e1+e2)>d.
The throttling of the sectional flow area within the auxiliary
discharge system 92 allows the system to be tuned so that certain
reflection waves may be produced by the exhaust gases therein
during high speed vessel operation in order to enhance engine
performance.
The above-described construction not only allows an amount of the
exhaust gases to quietly discharge the system through the auxiliary
passage arrangement 94 during low speed/idle operation; but
additionally, as a result of the relative flow sectional areas
employed, and the fact that the auxiliary outlets are located above
the water surface level L1 during high speed operation and, thus,
will not subject exiting gases to water induced back pressure, a
portion of the exhaust gases may readily pass therethrough when
operating the vessel at such higher speeds.
These exhaust gases exiting the auxiliary discharge system 94 will
be directed towards the water surface L1 since the auxiliary
discharge outlets are located opposite the water surface L1 during
high speed vessel operation. When these exhaust gases impinge upon
the water's surface the energy of the exhaust noise is dampened,
and so exhaust noise is thereby reduced.
Since the exhaust arrangement of the present invention helps to
smoothly direct the exhaust gases along the system, as by way of
the guide wall 86 at the joining pipe and the arched wall 93 at the
branching section 89 of the pipe 88; and, additionally, since a
portion of the exhaust gases are allowed to exit through the
auxiliary passage arrangement 92 even under high speed operating
conditions, the amount of exhaust gases which pass through the main
discharge arrangement 94 under high speed conditions will not
become excessively large as to overload the capacity of the main
discharge arrangement 94 and hinder engine performance. Therefore,
according to the construction described herein, it is not necessary
to increase the diameter of the high speed discharge outlet in
order to accommodate the quantity of exhaust gases generated during
high speed engine operation. So, the disadvantages of a larger
diameter hub, which might otherwise be necessitated in a through
the hub high speed discharge arrangement, are presently
avoided.
The foregoing description is, of course, only that of a preferred
embodiment of the invention, and various changes and modifications
may be made without departing from the spirit and scope of the
invention, as defined by the appended claims.
* * * * *